 /*******************************************************************************
  * Copyright (c) 2000, 2004 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Common Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/cpl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  *******************************************************************************/
 package org.eclipse.ui.internal;

 import java.util.*;

 import org.eclipse.core.runtime.*;
 import org.eclipse.core.runtime.Status;
 import org.eclipse.jface.util.ListenerList;
 import org.eclipse.ui.*;

 /**
  * This is used to store the most recently used (MRU) list
  * of perspectives for the entire workbench.
  */
 public class PerspectiveHistory {
     
     private static final int DEFAULT_DEPTH = 50;
     
     private ArrayList shortcuts;
     private IPerspectiveRegistry reg;
     private ListenerList listeners = new ListenerList();

     public PerspectiveHistory(IPerspectiveRegistry reg) {
         this.shortcuts = new ArrayList(DEFAULT_DEPTH);
         this.reg = reg;
     }

     public void addListener(IPropertyListener l) {
         listeners.add(l);
     }
     
     public void removeListener(IPropertyListener l) {
         listeners.remove(l);
     }
     
     private void fireChange() {
         Object [] array = listeners.getListeners();
         for (int i = 0; i < array.length; i++) {
             IPropertyListener element = (IPropertyListener)array[i];
             element.propertyChanged(this, 0);
         }
     }
     
     public IStatus restoreState(IMemento memento) {
         IMemento [] children = memento.getChildren("desc"); //$NON-NLS-1$
 for (int i = 0; i < children.length && i < DEFAULT_DEPTH; i++) {
             IPerspectiveDescriptor desc =
                 reg.findPerspectiveWithId(children[i].getID());
             if (desc != null)
                 shortcuts.add(desc);
         }
         return new Status(IStatus.OK,PlatformUI.PLUGIN_ID,0,"",null); //$NON-NLS-1$
 }
     
     public IStatus saveState(IMemento memento) {
         Iterator iter = shortcuts.iterator();
         while (iter.hasNext()) {
             IPerspectiveDescriptor desc = (IPerspectiveDescriptor)iter.next();
             memento.createChild("desc", desc.getId()); //$NON-NLS-1$
 }
         return new Status(IStatus.OK,PlatformUI.PLUGIN_ID,0,"",null); //$NON-NLS-1$
 }

     public void add(String id) {
         IPerspectiveDescriptor desc = reg.findPerspectiveWithId(id);
         if (desc != null)
             add(desc);
     }
     
     public void add(IPerspectiveDescriptor desc) {
         // Avoid duplicates
 if (shortcuts.contains(desc))
             return;

         // If the shortcut list will be too long, remove oldest ones
 int size = shortcuts.size();
         int preferredSize = DEFAULT_DEPTH;
         while (size >= preferredSize) {
             size--;
             shortcuts.remove(size);
         }
         
         // Insert at top as most recent
 shortcuts.add(0, desc);
         fireChange();
     }
     
     public void refreshFromRegistry() {
         boolean change = false;
         
         Iterator iter = shortcuts.iterator();
         while (iter.hasNext()) {
             IPerspectiveDescriptor desc = (IPerspectiveDescriptor)iter.next();
             if (reg.findPerspectiveWithId(desc.getId()) == null) {
                 iter.remove();
                 change = true;
             }
         }
         
         if (change)
             fireChange();
     }

     /**
      * Copy the requested number of items from the history into
      * the destination list at the given index.
      *
      * @param dest destination list to contain the items
      * @param destStart index in destination list to start copying items at
      * @param count number of items to copy from history
      * @return the number of items actually copied
      */
     public int copyItems(List dest, int destStart, int count) {
         int itemCount = count;
         if (itemCount > shortcuts.size())
             itemCount = shortcuts.size();
             
         for (int i = 0; i < itemCount; i++)
             dest.add(destStart + i, shortcuts.get(i));
             
         return itemCount;
     }

     //for dynamic UI
 public void removeItem(Object item) {
         for (int i = 0; i < shortcuts.size(); i++)
             if (shortcuts.get(i) == item) {
                 shortcuts.remove(i);
                 break;
             }
     }
 }


